Liquid ejector and liquid ejecting method

ABSTRACT

The present invention is directed to a liquid discharge apparatus adapted for discharging inks from discharge holes, which comprises a control unit ( 68 ) for controlling a discharge control unit ( 63 ), wherein the control unit controls the discharge control unit in such a manner that pulse current delivered to one of a pair of heating resistors ( 42   a ), ( 42   b ) is caused to be reference, and pulse current is delivered to the other heating resistor in the state where timing is shifted in a time of the range within 20% of supply time of pulse current serving as reference with respect to supply timing of pulse current serving as reference. Thus, it is possible to suppress unevenness or variation of impact positions of ink droplets discharged in the state where discharge direction has been changed. As a result, deterioration of picture quality resulting from color tone unevenness and/or white stripe, etc. is prevented. Thus, print operation can be performed at excellent picture quality.

TECHNICAL FIELD

The present invention relates to a liquid discharge apparatus and aliquid discharge method which are adapted for discharging droplets fromdischarge holes.

This Application claims priority of Japanese Patent Application No.2003-311625, filed on Sep. 3, 2003, the entirety of which isincorporated by reference herein.

BACKGROUND ART

Hitherto, as an apparatus adapted for discharging liquid, there areliquid discharge apparatuses of the ink jet type system which areadapted for discharging inks which are liquid from liquid dischargeportions with respect to a recording paper as object to record imagesand/or characters.

The liquid discharge apparatuses using ink jet system have the meritsthat running cost is low, and miniaturization of the apparatus andrealization of color print image are easy.

In the liquid discharge apparatuses using ink jet system, inks ofyellow, magenta, cyan and black, etc. are delivered from ink cartridgeto ink liquid chambers of liquid discharge portion, etc. The inks whichhave been delivered to the ink liquid chambers, etc. are pressed bypressure generated by pressure generating or producing element such asheating resistor, etc. disposed within the ink liquid chamber. As aresult, inks within the ink liquid chambers are discharged from verysmall ink discharge holes, so-called nozzles provided at the liquiddischarge portion. In concrete terms, inks within the ink chamber areheated by heating resistor disposed within the ink liquid chamber toproduce bubbles at inks on the heating resistor. By pressure produced bybubbles, inks are discharged from the nozzles to hit the inks which havebeen discharged onto recording paper as object, etc. to print imagesand/or characters.

As a liquid discharge apparatus employing the ink jet system, there is aprinter apparatus of the serial type in which ink cartridge is loaded orattached to liquid discharge head and the liquid discharge head is movedin width direction of the recording paper, i.e., in a directionsubstantially perpendicular to carrying direction of the recording paperto thereby hit inks of predetermined colors onto the recording paper.Moreover, there is a liquid discharge apparatus of the so-called linehead type in which substantially the same range as width of therecording paper is caused to be discharge range of the ink, i.e., inksare discharged from nozzles of liquid discharge portions arranged inwidth direction of the recording paper.

In the liquid discharge apparatus of the serial type, when the liquiddischarge head is moved in a direction substantially perpendicular tocarrying direction of the recording paper, traveling operation of therecording paper is stopped to discharge inks with respect to therecording paper in a stop state while moving the liquid discharge headto repeat such discharge operation to thereby perform print operation.On the other hand, in the liquid discharge apparatus of the line headtype, the liquid discharge head is generally fixed to discharge inksfrom the liquid discharge head with respect to continuously travelingrecording paper to hit those inks to thereby perform print operation.For this reason, since the liquid discharge apparatus of the line headtype is adapted so that the liquid discharge head is not moved unlikethe liquid discharge apparatus of the serial type, it becomes possibleto perform high speed print operation as compared to the printerapparatus of the serial type.

Moreover, in the liquid discharge apparatus of the line head type,because it is unnecessary to move the liquid discharge head, respectiveink cartridges can be enlarged. As a result, ink capacity of the inkcartridge can be increased. In such liquid discharge apparatus of theline head type, since the liquid discharge head is not moved,simplification of the configuration can be realized. Thus, it becomespossible to integrally provide respective ink cartridges and liquiddischarge head.

Meanwhile, in the above-described liquid discharge apparatus of the linehead type, print accuracy of image and/or character, etc. depend uponaccuracy of the timing at which ink is hit onto traveling recordingpaper. Explanation will be given in concrete terms. There takes placethe problem that when, e.g., traveling speed of the recording paper ishigh, print operation is performed in the state where recorded imagesand/or characters, etc. are expanded in carrying direction of therecording paper, and while when traveling speed of the recording paperis low, print operation is performed in the state where recorded imagesand/or characters, etc. are contracted in carrying direction of therecording paper.

In order to solve such problem, in the liquid discharge apparatus of theline head type, e.g., servo motor, etc. is used for control of motor fortraveling recording paper, etc. Namely, traveling speed is caused to beconstant so that unevenness does not take place in traveling speed ofthe recording paper to thereby control the timing at which ink is hitonto the recording paper.

Even in the case where servo motor as described above, etc. is used,while expansion and/or contraction of image, etc. are eliminated, thereis the possibility that when there slightly exists error of severalmicrons at impact timing of ink onto the recording paper, color toneunevenness, i.e., unevenness of density of color may take place incarrying direction of the recording paper. In concrete terms, whencontrol of traveling speed of the recording paper by servo motor isdelayed slightly by several microns, color tone becomes thick at thisportion. On the other hand, when control of the traveling speed of therecording paper by the servo motor becomes fast slightly by severalmicrons, color tone becomes thin at this portion. Further, when controlof traveling speed of the recording paper becomes fast at level ofseveral ten microns or several hundred microns, there take place aportion in which no ink is hit, i.e., so-called white stripe would takeplace over the range in a direction substantially perpendicular tocarrying direction of the recording paper.

On the other hand, in the liquid discharge apparatus of the serial type,in stopping traveling operation of the recording paper to perform printoperation, print operation in which so-called overlap portion isprovided is performed in such a manner that the previous print portionand current print portion overlap with each other within a predeterminedrange at the boundary portion thereof to thereby prevent color toneunevenness or white stripe from taking place in carrying direction ofthe recording paper. In the liquid discharge apparatus of the serialtype, color tone unevenness and/or white stripe, etc. can be suppressed,but there is the problem that the above-mentioned overlap portion isprovided so that time required for print operation is elongated, and/orquantity of ink used for print operation is increased.

In order to solve problems as described above, it is proposed in theJapanese Patent Application Laid Open No. 2000-185403 publication thatthere is employed (used) such a configuration disclosed in the U.S. Pat.No. 5,172,139 specification, i.e., the configuration in which pluralheating resistors are provided so that they are face-symmetrical witheach other at a plane including center line of nozzle at a positionopposite to nozzle of the liquid discharge portion which discharges inksto allow heat quantities of respective heating resistors to be differentfrom each other to thereby control discharge direction of ink.

In the case of the configuration disclosed in the Japanese PatentApplication Laid Open No. 2000-185403 publication, in the case whereheat quantities of respective heating resistors are not suitable, inkmight not be discharged in a desired discharge direction. As a result,picture quality may be lowered. In practical sense, as in a liquiddischarge portion (element) 201 shown in FIG. 22, in the case whereenergies delivered to the respective heating resistors 202 are notsuitable, balance of size of bubbles 204, etc. that the respectiveheating resistors 202 produce at ink 203 becomes poor. Namely, in thisliquid discharge portion 201, there is the possibility that balance ofpressure for pressing ink 203 on respective heating resistors 202becomes unstable so that discharge direction of ink may be diverse.

Moreover, in the liquid discharge portion 201, in the case where balanceof pressure for pressing ink 203 on respective heating resistors 202becomes unstable, there are instances where discharge angle θ of inkdroplet i from the nozzles 205 becomes too small. In this case, in theliquid discharge portion 201, since discharge angle θ of ink droplet ibecomes too small, ink droplet i comes into contact with edge portion205 a of the nozzle 205 when the ink droplet i is discharged from thenozzle 205. Further, the discharge direction is caused to be diverse.

From the above-mentioned facts, in the discharge portion (head) 201,there are instances where impact point is shifted when ink droplet i ishit upon the principal surface of the recording paper P, and color toneunevenness and/or white stripe, etc. take place so that picture qualitymay be lowered.

In view of the above, in the liquid discharge portion 201, it isimportant to suitably control heat quantities of respective heatingresistors 202 for discharging ink droplet i from the nozzle 205, i.e.,energy quantities, etc. such as current, etc. delivered to respectiveheating resistors 202 for the purpose of heating respective heatingresistors 202.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

An object of the present invention is to provide a novel liquiddischarge apparatus and a novel liquid discharge method which caneliminate problems that prior arts as described above have.

Another object of the present invention is to provide a liquid dischargeapparatus and a liquid discharge method which are adapted for preventingpressure balance for pressing liquid produced by respective pressuregenerating elements from being uncontrollable to thereby have ability toprevent lowering of picture quality.

The liquid discharge apparatus according to the present inventioncomprises discharge control means including a liquid chamber for storingliquid therewithin, two pressure generating elements or more provided atthe liquid chamber and serving to press liquid stored within the liquidchamber, and discharge holes for discharging liquid which has beenpressed by the respective pressure generating elements in the state ofdroplet from the liquid chamber thus to control supply timings andsupply times of energies to respective pressure generating elements tocontrol discharge angle when droplet is discharged from the dischargehole. Here, the discharge control means is adapted so that, with energydelivered to one of the respective pressure generating elements being asreference, the discharge control means delivers energy to the otherpressure generating element in the state where timing is shifted in atime of the range within 20% of supply time of energy serving asreference with respect to supply timing of energy serving as reference.

The liquid discharge apparatus according to the present invention isadapted to deliver energy to other pressure generating element at atiming which is substantially the same as reference energy, or deliversenergy thereto in the state where time is shifted within the range of20% of the time period during which reference energy is delivered withrespect to reference energy so that energy is delivered to respectivepressure generating elements at a suitable timing. Thus, it is possibleto discharge liquid in a desired direction from the discharge hole.

The liquid discharge method according to the present invention isdirected to a liquid discharge method for a liquid discharge apparatusincluding a liquid chamber for storing liquid therewithin, two pressuregenerating elements or more provided at the liquid chamber and servingto press liquid stored within the liquid chamber, and discharge holesfor discharging liquid which has been pressed by the respective pressuregenerating elements in the state of droplet from the liquid chamber,wherein energy delivered to one of respective pressure generatingelements is caused to be reference, and energy is delivered to the otherpressure generating element in the state where timing is shifted in atime of the range within 20% of supply time of energy serving asreference with respect to supply timing of energy serving as referenceto control discharge angle when the droplet is discharged from thedischarge hole.

In the liquid discharge method according to the present invention,energy is delivered to other pressure generating element at a timingwhich is substantially the same as that of reference energy, or energyis delivered thereto in the state where time is shifted in the rangewithin 20% of time period during which reference energy is deliveredwith respect to reference energy so that energy is delivered, at asuitable timing, to respective pressure generating elements. From thisfact, it is possible to discharge droplet from discharge hole toward adesired direction.

In accordance with the liquid discharge apparatus and the liquiddischarge method according to the present invention, shift of impactpoint of discharged droplet is also suppressed. Thus, print operationhaving excellent picture quality can be performed.

Still further objects of the present invention and practical meritsobtained by the present invention will become more apparent from thedescription of the embodiments which will be given below with referenceto the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a liquid discharge apparatusaccording to the present invention.

FIG. 2 is a perspective view showing ink jet print head cartridge usedin the liquid discharge apparatus.

FIG. 3 is a cross sectional view showing ink jet print head cartridge.

FIGS. 4A and 4B show an ink supply portion when ink cartridge is loadedinto ink jet print head cartridge, wherein FIG. 4A is a model viewshowing the state where the supply hole is closed, and FIG. 4B is amodel view showing the state where the supply hole is opened.

FIG. 5 is a cross sectional view showing the relationship between inkcartridge and ink discharge head which constitute the ink jet print headcartridge.

FIGS. 6A and 6B show valve mechanism at connection portion of inkcartridge, wherein FIG. 6A is a cross sectional view showing the statewhere the valve is closed, and FIG. 6B is a cross sectional view showingthe state where the valve is opened.

FIG. 7 is an exploded perspective view showing ink discharge head of theink jet print head cartridge.

FIG. 8 is a plan view showing ink discharge head.

FIG. 9 shows the state where the ink discharge head discharges inkdroplet, and is a cross sectional view showing the state where inkbubbles having substantially the same size are formed within ink liquidchamber.

FIG. 10 explains the state where the ink discharge head discharges inkdroplet, and is a cross sectional view showing the state where inkdroplet is discharged toward the portion substantially immediately belowfrom nozzles by two ink bubbles.

FIG. 11 shows the state where the ink discharge head discharges inkdroplet, and is a cross sectional view showing the state where inkbubbles having different sizes are formed within ink liquid chamber.

FIG. 12 shows the state where the ink discharge head discharges inkdroplet, and is a cross sectional view showing the state where inkdroplet is discharged in substantially oblique direction from nozzles bytwo ink bubbles.

FIG. 13 is a side view perspectively showing a portion of the liquiddischarge apparatus.

FIG. 14 is a block diagram showing a control circuit of the liquiddischarge apparatus.

FIG. 15 is a circuit diagram showing discharge control unit of thecontrol circuit.

FIGS. 16A to 16C show that discharge control unit controls dischargedirection of ink droplet, wherein FIG. 16A is a cross sectional viewshowing that ink droplet is discharged toward the direction of theportion positioned substantially immediately below, FIG. 16B is a crosssectional view showing the state where ink droplet is discharged in onesubstantially oblique direction of width direction of recording paperwith nozzle being as center, and FIG. 16C is a cross sectional view forexplaining the state where ink droplet is discharged in othersubstantially oblique direction of width direction of recording paperwith nozzle being as center.

FIG. 17 is a characteristic diagram showing the relationship betweenshift quantity of current supply timing of a pair of heating resistorswhich constitute the ink discharge head and discharge angle.

FIGS. 18A to 18F are model views showing impact points of ink dropletdischarged from the nozzle when pulse current is delivered to a pair ofheating resistors at ink discharge head in the state where timing isshifted, wherein FIG. 18A shows impact points when shift quantity ofcurrent supply timing is 0%, FIG. 18B shows impact points when shiftquantity of current supply timing is 7.5%, FIG. 18C shows impact pointswhen shift quantity of current supply timing is 13%, FIG. 18D showsimpact points when shift quantity of current supply timing is 20%, FIG.18E shows impact points when shift quantity of current supply timing is21%, and FIG. 18F shows impact points when shift quantity of currentsupply timing is 23%.

FIG. 19 is a flowchart for explaining print operation of the liquiddischarge apparatus according to the present invention.

FIG. 20 is a side view partially perspectively showing the state wherehead cap opening/closing mechanism is opened in the liquid dischargeapparatus according to the present invention.

FIGS. 21A to 21C show other examples of ink discharge head, wherein FIG.21A is a plan view showing the state where heating resistors arearranged in parallel in carrying direction of recording paper, FIG. 21Bis a plan view showing the state where three heating resistors areprovided within ink chamber, and FIG. 21C is a plan view showing thestate where four heating resistors are provided within the ink chamber.

FIG. 22 is a cross sectional view showing, in a model manner, aconventional liquid discharge portion (element).

BEST MODE FOR CARRYING OUT THE INVENTION

A liquid discharge apparatus and a liquid discharge method according tothe present invention will now be explained with reference to theattached drawings.

As shown in FIG. 1, a printer apparatus 1 which is a liquid dischargeapparatus of the ink jet system to which the present invention isapplied serves to discharge inks, etc. with respect to recording papersP traveling in a predetermined direction to print images and/orcharacters. The printer apparatus 1 is directed to the printer apparatusof the so-called line head type in which ink discharge holes (nozzles)are arranged in parallel in substantially line form in width directionof recording paper P, i.e., in a direction indicated by arrow W in FIG.1 in correspondence with print width of the recording paper P.

The printer apparatus 1 according to the present invention comprises anink jet print head cartridge (hereinafter referred to as unit headcartridge) 2 for discharging ink 4, and a printer body 3 for loading orattaching the head cartridge 2. In the printer apparatus 1, the headcartridge 2 is detachable with respect to the printer body 3, and inkcartridges 11 y, 11 m, 11 c, 11 k serving as ink supply source arefurther detachably loaded with respect to the head cartridge 2. In theprinter apparatus 1, ink cartridge 11 y within which yellow ink isfilled, ink cartridge 11 m within which magenta ink is filled, inkcartridge 11 c within which cyan ink is filled, and ink cartridge 11 kwithin which black ink is filled can be used. In addition, the headcartridge 2 detachable with respect to the printer body 3, and inkcartridges 11 y, 11 m, 11 c, 11 k detachable with respect to the headcartridge 22 are caused to be as consumable supplies.

In such printer apparatus 1, a tray 55 a for accommodating recordingpapers P in a stacked manner is loaded at a tray loading unit 5 providedat the bottom surface side of the front face of the printer body 3,thereby making it possible to feed or deliver recording papers Paccommodated within the tray 55 a into the printer body 3. When the tray55 a is loaded into the tray loading unit 5 of the front face of theprinter body 3, recording paper P is fed from a paper feed hole 55toward the rear surface side of the printer body 3 by a paper feed/ejectmechanism (see FIG. 13). The carrying direction of the recording paper Pwhich has been sent toward the rear surface side of the printer body 3is inverted by inverting roller 83 (see FIG. 13). Thus, the recordingpaper P is sent from the rear surface side of the printer body 3 towardthe front surface side thereof at the upper side of outgoing path. For atime period until recording paper P sent from the rear surface side ofthe printer body 3 toward the front surface side is ejected from a papereject hole 56 provided at the front surface of the printer body 3, printdata corresponding to character data and/or image data inputted from aninformation processing unit (processor) 69 such as personal computer,etc. (see FIG. 14) are printed as characters and/or images onto therecording paper P.

The head cartridge 2 for performing print operation with respect torecording paper P is loaded from the upper surface side of the printerbody 3, i.e., from the direction indicated by arrow A in FIG. 1 todischarge ink 4 with respect to the recording paper P traveling by thepaper feed/eject mechanism 54 to perform print operation. In thisexample, the head cartridge 2 detachable with respect to the printerbody 1 constituting the above-described printer apparatus 1 and inkcartridges 11 y, 11 m, 11 c, 11 k detachable to the head cartridge 2will be first explained with reference to the attached drawings.

The head cartridge 2 serves to change ink 4 serving as conductive liquidinto fine particles by pressure that pressure generating or producingmeans using, e.g., electrical-thermal transform system orelectrical-mechanical transform system, etc. to discharge the liquid inparticle form to spray them in the state of droplet onto the principalsurface of object such as recording paper P, etc. In concrete terms, asshown in FIGS. 2 and 3, the head cartridge 2 includes a cartridge body21, wherein ink cartridges 11 y, 11 m, 11 c, 11 k serving as vesselwithin which ink 4 is filled are loaded with respect to the cartridgebody 21. It is to be noted that, in the following description, ink,cartridges 11 y, 11 m, 11 c, 11 k will be simply referred to as inkcartridge 11 as occasion may demand.

As shown in FIG. 3, the ink cartridge 11 detachable to the headcartridge 2 includes a cartridge vessel 12 molded by injection-moldingresin material, etc. such as polypropylene, etc. having strength and/orink resistance characteristic. The cartridge vessel 12 is formed so asto take substantially rectangular shape in which size in lengthdirection is caused to be the same size as that of width direction ofrecording paper P used, and is caused to be of the configuration toincrease, as large as possible, ink capacity stored therewithin.

In concrete terms, at the cartridge vessel 12 constituting the inkcartridge 11, there are provided an ink accommodating portion 13 foraccommodating ink 4, an ink supply portion 14 for supplying ink 4 fromthe ink accommodating portion 13 to the cartridge body 21 of the headcartridge 2, an external communicating hole 15 for taking air from theexternal into the ink accommodating portion 13, an air introduction path16 for introducing air which has been taken from the externalcommunication hole 15 into the ink accommodating portion 13, a storageportion 17 for temporarily storing ink 4 between the externalcommunicating hole 15 and the air introduction path 16, and a holdingprojection portion 18 and an engagement step portion 19 for holding theink cartridge 11 at the cartridge body 21.

The ink accommodating portion 13 forms a space for accommodating ink 4by material having high sealing property. The ink accommodating portion13 is formed so as to take substantially rectangular shape, and isformed so that size in length direction is caused to be substantiallythe same size as size of width direction of the recording paper P used,i.e., width direction W of the recording paper P shown in FIG. 3.

The ink supply portion 14 is provided substantially at the centralportion of the lower side of the ink accommodating portion 13. The inksupply portion 14 is nozzles in substantially projection shape, whichcommunicates with the ink accommodating portion 13, and the front end ofthe nozzle is fitted into the connecting unit 26 of the head cartridge 2which will be described later to thereby connect the cartridge vessel 12of the ink cartridge 2 and the cartridge body 21 of the head cartridge2.

At the ink supply portion 14, as shown in FIGS. 4A and 4B, there isprovided a supply hole 14 b for supplying ink 4 onto bottom surface 14 aof the ink cartridge 11. At the bottom surface 14 a, there are provideda valve 14 c for opening/closing the supply hole 14 b, a coil spring 14d for biasing the valve 14 c in a direction to close the supply hole 14b, and an opening/closing pin 14 e for opening/closing the valve 14 c.At the supply hole 14 b for supplying ink 4, which is connected to theconnecting portion 26 of the head cartridge 2, as shown in FIG. 4A, thevalve 14 c is biased and closed in a direction to close the supply hole14 b by biasing force of the coil spring 14 d serving as biasing memberat the stage before the ink cartridge 11 is loaded into the cartridgebody 21 of the head cartridge 2. Further, when the ink cartridge 11 isloaded into the cartridge body 21, the opening/closing pin 14 e ispushed upward in a direction opposite to biasing direction of the coilspring 14 d by the upper portion of the connecting portion 26 of thecartridge body 21 constituting the head cartridge 2. Thus, theopening/closing pin 14 c which has been pushed upwardly pushes the valve14 c upwardly against biasing force of the coil spring 14 d to open thesupply hole 14 b. In a manner as stated above, the ink supply portion 14of the ink cartridge 11 is connected to the connecting portion 26 of thehead cartridge 2 to allow the ink accommodating portion 13 and inkstorage portion 31 to communicate with each other so that there resultsthe state where supply of ink 4 to the ink cartridge portion 31 can bemade.

Moreover, when the ink cartridge 11 is pulled (drawn) out from theconnecting portion 26 of the head cartridge 2 side, i.e., the inkcartridge 11 is detached from the loading portion 22 of the headcartridge 2, pushing-up state by the opening/closing pin 14 e of thevalve 14 c is released. As a result, the valve 14 c is moved in abiasing direction of the coil spring 14 d to close the supply hole 14 b.Thus, immediately before the ink cartridge 11 is loaded into thecartridge body 21, it is possible to prevent ink 4 within inkaccommodating portion 13 from being leaked even in the state where thefront end portion of the ink supply portion 14 is directed downwardly.Further, when the ink cartridge 11 is pulled (drawn) out from thecartridge body 21, since the valve 14 c immediately closes the supplyhole 14 b, it is possible to prevent ink 4 from being leaked from thefront end of the ink supply portion 14.

As shown in FIG. 3, an external communicating hole 15 is a ventilationhole for taking air from the ink cartridge 11 external into the inkaccommodating portion 13. Also when the ink cartridge 11 is loaded intothe loading portion 22 of the head cartridge 2, the externalcommunicating hole 15 is provided at the upper surface, i.e., atsubstantially the center of the upper surface of the cartridge vessel 12which is the position facing to the external at the time of loading withrespect to the loading portion 22. When the ink cartridge 11 is loadedat the cartridge body 21 so that ink 4 flows downwards from the inkaccommodating portion 13 toward the cartridge body 21 side, the externalcommunicating hole 15 takes air corresponding to the quantity that ink 4within the ink accommodating unit 13 is decreased from the external intothe ink cartridge 11.

An air introduction path 16 allows the ink accommodating portion 13 andthe external communicating hole 15 to communicate with each other tointroduce air which has been taken in from the external communicatinghole 15 into the ink accommodating portion 13. Thus, when the inkcartridge 11 is loaded at the cartridge body 21, even if ink isdelivered to the cartridge body 21 of the head cartridge 2 so that ink 4within the ink accommodating portion 13 is decreased and the insidethereof is placed in decompressed state, air is introduced to the inkaccommodating portion 13 by the air introduction path 16. From thisfact, the internal pressure is kept in equilibrium state thus to haveability to suitably deliver ink 4 to the cartridge body 21.

The storage portion 17 is provided between the external communicatinghole 15 and the air introduction path 16, and serves to temporarilystore ink 4 so that ink 4 does not suddenly flow out to the externalwhen ink 4 is leaked from the air introduction path 16 communicatingwith the ink accommodating portion 13. The storage portion 17 is formedso as to take substantially diamond shape in which longer diagonal lineis caused to be length direction of the ink accommodating portion 13,and is adapted so that the air introduction path 16 is provided at thesummit portion positioned at the lowest side of the ink accommodatingportion 13, i.e., at the lower side on the shorter diagonal line. Thus,ink 4 admitted from the ink accommodating portion 13 can be returned tothe ink accommodating portion 13 for a second time.

A holding projecting portion 18 is a projection provided at one sidesurface of short side of the ink cartridge 11, and is engaged with anengagement hole 24 a formed at a latch lever 24 of the cartridge body 21of the head cartridge 2. The holding projecting portion 18 is adapted sothat the upper surface thereof is formed at such a plane substantiallyperpendicular to the side surface of the ink accommodating portion 13,and the lower surface thereof is formed in a manner inclined from theside surface toward the upper surface.

An engagement step portion 19 is provided at the upper portion of theside surface opposite to the side surface where the engagementprojection 18 is provided of the ink cartridge 11. The engagement stepportion 19 is composed of an inclined surface 19 a of which one end isin contact with the upper surface of the cartridge vessel 12, and aplane 19 b continuous to the other side surface of the other end of theinclined surface 19 a and substantially in parallel to the upper surfacethereof. As the result of the fact that the engagement step portion 19is provided, the ink cartridge 11 is formed so that height of the sidesurface where the plane 19 b is provided is lower than the upper surfaceof the cartridge vessel 12 by one step, and is engaged with anengagement piece 23 of the cartridge body 21 at this step portion. Asthe result of the fact that the engagement step portion 19 is engagedwith an engagement piece 23 of the loading portion 22 side of the headcartridge 2 provided at the side surface of the insertion end side whenthe ink cartridge 11 is inserted into the loading portion 22 of the headcartridge 2, the engagement step portion 19 serves as rotational fulcrumportion when the ink cartridge 11 is loaded into the loading portion 22.

The ink cartridge 11 of the configuration as stated above comprises, inaddition to the above-described components, e.g., remaining quantitydetecting portion (unit) for detecting the remaining quantity of ink 4within the ink accommodating portion 13, and a discrimination portion(unit) for discriminating between ink cartridges 11 y, 11 m, 11 c, 11 k,etc.

Then, the head cartridge 2 to which ink cartridges 11 y, 11 m, 11 c, 11k within which inks 4 of yellow, magenta, cyan and black areaccommodated are loaded, which has been constituted as described above,will be explained.

As shown in FIGS. 2 and 3, the head cartridge 2 is composed of theabove-described ink cartridge 11 and cartridge body 21. The cartridgebody 21 includes loading portions 22 y, 22 m, 22 c, 22 k (hereinaftersimply referred to as loading portion when the entirety thereof isindicated) to which ink cartridge 11 is loaded, an engagement piece 23and a latch lever 24 which are adapted for fixing the ink cartridge 11,a biasing member 25 for biasing the ink cartridge 11 in a taking-outdirection, a connecting portion 26 connected to the ink supply portion14 and supplied with ink 4, an ink discharge head 27 for discharginginks 4, and a head cap 28 for protecting the ink discharge head 27.

The upper surface of the loading portion 22 to which the ink cartridge11 is to be loaded is formed in a manner to take substantially recessedshape as insertion/withdrawal opening of the ink cartridge 11 so thatthe ink cartridge 11 is loaded thereto. In this example, four inkcartridges 11 are accommodated in line in a direction substantiallyperpendicular to width direction of the recording paper P, i.e., incarrying direction of the recording paper P. As the result of the factthat the ink cartridge 11 is accommodated at the loading portion 22, theloading portion 22 is provided in the state elongated in a direction ofprint width similarly to the ink cartridge 11. The ink cartridge 11 isaccommodated and loaded at the cartridge body 21.

As shown in FIG. 2, the loading portion 22 is a portion to which inkcartridge 11 is loaded. The portion where ink cartridge 11 y for yellowis loaded is caused to be a loading portion 22 y, the portion where inkcartridge 11 m for magenta is loaded is caused to be a loading portion22 m, the portion where ink cartridge 11 c for cyan is loaded is causedto be a loading portion 22 c, and the portion where ink cartridge 11 kfor black is loaded is caused to be loading portion 22 k. The loadingportions 22 y, 22 m, 22 c, 22 k are respectively partitioned bypartition walls 22 a. In this example, because use quantity of ink isgenerally many, the ink cartridge 11 c for black is formed to be thickas described above so that the internal capacity becomes large.Therefore, width of the ink cartridge 11 k is greater than those ofother ink cartridges 11 y, 11 m, 11 c. For this reason, the loadingportion 22 k is broader than other loading portions 22 y, 22 m, 22 c incorrespondence with thickness of the ink cartridge 11 k.

Moreover, at the opening end of the loading portion 22 where the inkcartridge 11 is loaded, as shown in FIG. 3, there is provided anengagement piece 23. The engagement piece 23 is provided at one end edgein a length direction of the loading portion 22, and is engaged withengagement step portion 19 of the ink cartridge 11. The ink cartridge 11is obliquely inserted into the loading portion 22 with the engagementstep portion 19 side of the ink cartridge 11 being as insertion end, andcan be loaded into the loading portion 22 in such a manner to rotate theside where the engagement step portion 19 is not provided of the inkcartridge 11 toward the loading portion 22 side with engagement positionbetween engagement step portion 19 and engagement piece 23 being asfulcrum of rotation. Thus, the ink cartridge 11 can be easily loaded atthe loading portion 22.

The latch lever 24 is formed by bending leaf spring, and is provided atthe side surface opposite to the engagement piece 23 of the loadingportion 22, i.e., at the side surface of the other end in lengthdirection. The latch lever 24 is adapted so that the base end portionthereof is integrally provided at the bottom surface side of the sidesurface of the other end in length direction constituting the loadingportion 22, the front end side thereof is formed so that elasticdisplacement is performed in a direction close to the side surface oraway therefrom, and an engagement hole 24 a is formed at the front endside thereof. At the same time when the ink cartridge 11 is loaded intothe loading portion 22, the latch lever 24 is caused to undergo elasticdisplacement so that the engagement hole 24 a is engaged with theholding projection 18 of the ink cartridge 11 to prevent the inkcartridge 11 loaded at the loading portion 22 from slipping off from theloading portion 22.

A biasing member 25 is provided by bending leaf spring which biases theink cartridge 11 in a detachment direction thereof on the bottom surfaceof the side surface side corresponding to the engagement step portion 19of the ink cartridge 11. The biasing member 25 is an eject member whichhas a summit portion formed by bending, and is caused to undergo elasticdisplacement in a direction close to the bottom surface or awaytherefrom to press the bottom surface of the cartridge 11 by the summitportion to bias the ink cartridge 11 loaded at the loading portion 22 ina taking-out direction from the loading portion 22. When engagementstate between the engagement hole 24 a and the holding projectingportion 18 of the latch lever 24 is released, the biasing member 25ejects the ink cartridge 11 from the loading portion 23.

At substantially center in a length direction of respective loadingportions 22 y, 22 m, 22 c, 22 k, there are provided connecting portions26 to which ink supply portions 14 of the ink cartridges 11 y, 11 m, 11c, 11 k are connected when ink cartridges 11 y, 11 m, 11 c, 11 k areloaded into the loading portions 22 y, 22 m, 22 c, 22 k. The connectingportion 26 serves as an ink supply path for supplying ink 4 from the inksupply portion 14 to the ink discharge head 27.

In concrete terms, as shown in FIG. 5, the connecting portion 26includes an ink storage portion 31 for storing ink 4 supplied from theink cartridge 11, a sealing member 32 for sealing the ink supply portion14 connected to the connecting portion 26, a filter 33 for removingimpurities within the ink 4, and a valve mechanism 34 foropening/closing the supply path toward the ink discharge head 27.

The ink storage portion 31 is a space portion connected to the inksupply portion 14 and adapted for storing ink 4 delivered from the inkcartridge 11. The sealing member 32 is a member provided at the upperend of the ink storage portion 31, and serves to seal the portionbetween ink storage portion 31 and ink supply portion 14 so that ink 4is not leaked toward the outside when the ink supply portion 14 of theink cartridge 11 is connected to the ink storage portion 31 of theconnecting portion 26. A filter 33 serves to remove rubbishes such asdust, etc. which has been mixed into the ink 4 at the time ofloading/unloading of the ink cartridges 11, etc., and is provideddownwardly relative to the ink storage portion 31.

The valve mechanism 34 includes, as shown in FIGS. 6A and 6B, an inkflow-in path 34 a supplied with ink 4 from the ink storage portion 31,an ink chamber 34 b to which ink 4 is caused to flow in from the inkflow-in path 34 a, an ink flow-out path 34 c from which ink 4 is causedto flow out from the ink chamber 34 b, an opening portion 34 d providedbetween the ink flow-in path 34 a side and the ink flow-out path 34 cside of the ink chamber 34 b, a valve 34 e for opening/closing theopening portion 34 d, a biasing member 34 f for biasing the valve 34 ein a direction to close the opening portion 34 d, a negative pressureadjustment screw 34 g for adjusting strength of the biasing member 34 f,a valve shaft 34 h connected to the valve 34 e, and a diaphragm 34 iconnected to the valve shaft 34 h.

The ink flow-in path 34 a is a supply path connected to the inkaccommodating portion 13 so as to have ability to deliver ink 4 withinthe ink accommodating portion 13 of the ink cartridge 11 through the inkstorage portion 31 to the ink discharge head 27. The ink flow-in path 34a is provided within the range from the bottom surface side of the inkstorage portion 31 to the ink chamber 34 b. The ink chamber 34 b is aspace portion so as to take substantially rectangular parallelepipedshape, which is formed integrally with the ink flow-in path 34 a, theink flow-out path 34 c and the opening portion 34 d, and is adapted sothat ink 4 is caused to flow in from the ink flow-in path 34 a to allowink 4 to flow out from the ink flow-out path 34 c through the openingportion 34 d. The ink flow-out path 34 c is a supply path supplied withink 4 through the opening portion 34 d from the ink chamber 34 b, and isfurther connected to the ink discharge head 27. The ink flow-out path 34c is extended from the bottom surface side of the ink chamber 34 b up tothe ink discharge head 27.

The valve 34 e is a valve for closing the opening portion 34 d to divideit into the ink flow-in path 34 a side and the ink flow-out path 34 cside, and is disposed within the ink chamber 34 b. The valve 34 e movesupwardly and downwardly by biasing force of a biasing member 34 f, arestoring force of a diaphragm 34 i connected through a valve shaft 34h, and negative pressure of ink 4 of the ink flow-out path 34 c side.When the valve 34 e is located at the position of the lower end, itcloses the opening portion 34 d in such a manner to separate the inkchamber 34 b into the ink flow-in path 34 a side and the ink flow-outpath 34 c side to interrupt supply of ink 4 to the ink flow-out path 34c. When the valve 34 e is located at the upper end against biasing forceof the biasing member 34 f, the valve 34 e permits supply of ink 4 tothe ink discharge head 27 without interrupting (separating) the inkchamber 34 b into the ink flow-in path 34 a side and the ink flow-out 34c side. It is to be noted that although kind of material constitutingthe valve 34 e is not limited, the valve 34 e may be formed by, e.g.,rubber elastic body so-called elastomer, etc. in order to ensure highclosing property.

The biasing member 34 f is, e.g., compression coil spring, etc. andserves to connect negative pressure adjustment screw 34 g and valve 34 ebetween the upper surface of the valve 34 e and the upper surface of theink chamber 34 b to bias the valve 34 e by biasing force in a directionto close the opening portion 34 d. The negative pressure adjustmentscrew 34 g is a screw for adjusting biasing force of the biasing member34 f, and serves to adjust the negative pressure adjustment screw 34 gto thereby have ability to adjust biasing force of the biasing member 34f. Thus, although the detail will be described later, the negativepressure adjustment screw 34 g can adjust negative pressure of ink 4which operates valve 34 e for opening/closing the opening portion 34 dalthough the detail thereof will be described later.

A valve shaft 34 h is a shaft provided in order to connect the valve 34e connected to one end thereof and diaphragm 34 i connected to the otherend thereof to perform motion. The diaphragm 34 i is a thin elasticplate connected to the other end of the valve shaft 34 h. The diaphragm34 i consists of one principal surface of the ink flow-out path 34 cside of the ink chamber 34 b and the other principal surface in contactwith air, and is caused to undergo elastic displacement toward the airside and the ink flow-out path 34 c side by air pressure and negativepressure of ink 4.

In the valve mechanism 34 as stated above, as shown in FIG. 6A, thevalve 34 e is pressed by biasing force of the biasing member 34 f andbiasing force of the diaphragm 34 i so as to close the opening portion34 d of the ink chamber 34 b. Further, in the case where ink 4 isdischarged from the ink discharge head 27, when negative pressure of theink 4 of the ink chamber 34 b of the ink flow-out path 34 c side dividedat the opening portion 34 d is increased, the diaphragm 34 i is pushedupwardly by negative pressure of the ink 4 and air as shown in FIG. 6Bto push upwardly the valve 34 e against biasing force of the biasingmember 34 f along with the valve shaft 34 h. At this time, the openingportion 34 d between the ink flow-in path 34 a side and the ink flow-outpath 34 c side of the ink chamber 34 b is opened. Thus, ink 4 isdelivered from the ink flow-in path 34 a side toward the ink flow-outpath 34 c side. Further, negative pressure of the ink 4 is lowered. As aresult, the diaphragm 34 i is restored to original form by restoringforce to pull downwardly valve 34 e along with valve shaft 34 h bybiasing force of the biasing member 34 f so that the ink chamber 34 b isclosed. In a manner as stated above, at the valve mechanism 34, whennegative pressure is increased every time ink 4 is discharged, theabove-described operation is repeated.

At the connecting portion 26, when ink 4 within the ink accommodatingchamber 13 is delivered to the ink chamber 34 b, ink 4 within the inkaccommodating portion 13 is decreased. However, at this time, air isadmitted from the air introduction path 16 into the ink cartridge 11.The air which has been admitted into the ink cartridge 11 is sent towardthe upper portion of the ink cartridge 11. Thus, the state returns tothe state where ink droplet i is discharged from nozzle 44 a which willbe described later so that there results equilibrium state. At thistime, there results equilibrium state as the state where ink 4 hardlyexists within the air introduction path 16.

As shown in FIG. 5, the ink discharge head 27 is disposed along thebottom surface of the cartridge body 21, and is adapted so that nozzles44 a, which will be described later, serving as an ink discharge holefor discharging ink droplet i delivered from the connecting portion 26are caused to take substantially line shape in width direction of therecording paper P, i.e., in a direction indicated by arrow W in FIG. 5every respective colors.

As shown in FIG. 2, the head cap 28 is a cover provided for the purposeof protecting the ink discharge head 27, and is detached from the inkdischarge head 27 when print operation is performed. The head cap 28includes a groove portion 28 a provided in opening/closing direction,and a cleaning roller 28 b provided in a length direction and forabsorbing excess ink 4 attached to the discharge surface 27 a of the inkdischarge head 27. At the time of opening/closing operation, the headcap 28 is adapted to be opened or closed in short direction of the inkcartridge 11 along the groove portion 28 a. At this time, as the resultof the fact that the cleaning roller 28 b rotates while being in contactwith the discharge surface 27 a of the ink discharge head 27, it absorbsexcess ink 4 to clean the discharge surface 27 a of the ink dischargehead 27. As the cleaning roller 28 b, e.g., member having high waterabsorption property is used. In addition, when print operation is notperformed, the head cap 28 serves to prevent ink 4 within the inkdischarge head 27 from being dried.

The head cartridge 2 having a configuration as described abovecomprises, in addition to the above-described components, e.g., aremaining quantity detecting portion (unit) for detecting ink remainingquantity within ink cartridge 11, and an ink presence/absence detectingportion (unit) for detecting presence or absence of ink 4 when the inksupply unit 14 is connected to the connecting unit 26.

As shown in FIGS. 7 and 8, in correspondence with inks 4 of respectivecolors, the above-described ink discharge head 27 includes a substrate41 serving as base, pairs of heating resistors 42 a, 42 b provided inparallel in a direction substantially perpendicular to carryingdirection of the recording paper P, i.e., in width direction of therecording paper P, a film 43 for preventing leakage of ink 4, a nozzlesheet 44 provided with a large number of nozzles 44 a from which inks 4are discharged in the state of droplet, an ink liquid chamber 45surrounding by these components and serving as a space supplied with ink4, and an ink flow path 46 for supplying inks 4 to the ink liquidchamber 45.

The substrate 41 is a semiconductor substrate of silicon, etc. and isadapted so that pairs of heating resistors 42 a, 42 b are formed on oneprincipal surface 41 a thereof and the respective pairs of heatingresistors 42 a, 42 b are connected to discharge control unit which willbe described later on the substrate 41. The discharge control unit 63 isan electric circuit constituted by logic ICs (Integrated Circuits)and/or driver transistors, etc.

The pair of heating resistors 42 a, 42 b are pressure generatingelements which are heated by pulse current delivered from the dischargecontrol unit 63 to heat inks 4 within the ink liquid chamber 45 toincrease internal pressure. Further, inks 4 heated by the pair ofheating resistors 42 a, 42 b are discharged in the state of droplet fromnozzles 44 a provided at nozzle sheet 44 which will be described later.

The film 43 is laminated on one principal surface 41 a of the substrate41. The film 43 consists of, e.g., dry film resist of the exposurehardening type. The film 43 is laminated substantially over oneprincipal surface 41 a of the substrate 41. Thereafter, unnecessaryportions are removed by photolithographic process. Thus, the film 43 isformed in a manner to surround the pair of heating resistors 42 a, 42 bin substantially recessed form. At the film 43, portions which surroundrespective pairs of heating resistors 42 a, 42 b form a portion of theink liquid chamber 45.

The nozzle sheet 44 is a sheet shaped member having thickness of about10 μm to 15 μm where nozzles 44 a for discharging ink droplet i areformed, and is laminated on the surface opposite to the circuitsubstrate 41 of the film 43. The nozzles 44 a are very small holeshaving diameter of about 15 μ to 18 μm opened in circular shape at thenozzle sheet 44, and are disposed in a manner opposite to the pairs ofheating resistors 42 a, 42 b. In this example, the nozzle sheet 44constitutes a portion of the ink liquid chamber 45.

The ink liquid chamber 45 is a space portion surrounded by the substrate41, the pairs of heating resistors 42 a, 42 b, the film 43 and thenozzle sheet 44, and is a space adapted for storing ink 4 delivered fromthe ink flow path 46. The ink 4 within ink liquid chamber 45 is heatedby the pairs of heating resistors 42 a, 42 b so that internal pressureis raised.

The ink flow path 46 is connected to the ink flow-out path 34 c of theconnecting portion 26. Thus, ink 4 is delivered from the ink cartridge11 connected to the connecting portion 26 to form flow path for sendingout ink 4 to respective ink liquid chambers 45 communicating with theink flow path 46.

Namely, the ink flow path 46 and the connecting portion 26 are caused tocommunicate with each other. Thus, inks 4 delivered from the inkcartridge 11 flow into the ink flow path 46 and are filled into the inkliquid chamber 45.

At the above-described one ink discharge head 27, pairs of heatingresistors 42 a, 42 b are provided every ink liquid chamber 45. There areprovided about 100 to 5000 ink liquid chambers 45 in which such pair ofheating resistors 42 a, 42 b are provided every respective color inkcartridges 11. Further, at the ink discharge head 27, by instructionfrom the control unit 68 of the printer apparatus 1, these pairs ofheating resistors 42 a, 42 b are suitably selected and are heated. Theink 4 within the ink liquid chamber 45 corresponding to heated pair ofheating resistors 42 a, 42 b is caused to be discharged in the state ofdroplet from corresponding nozzle 44 a to the ink liquid chamber 45.

Namely, at the ink discharge head 27, ink 4 delivered from ink flow path46 connected to the ink discharge head 27 is filled within the inkliquid chamber 45. Further, pulse current is caused to flow for shorttime, e.g., 1 to 3 μsec. at the pair of heating resistors 42 a, 42 b.Thus, the pair of heating resistors 42 a, 42 b are respectively andrapidly heated. As a result, ink 4 of the portion in contact with thepair of heating resistors 42 a, 42 b is headed. Thus, ink bubbles ofvapor phase are produced. Ink 4 of a certain volume is pressed byexpansion (swelling) of the ink bubbles (ink 4 is boiled). Thus, ink 4having capacity equivalent to the ink 4 which has been pressed onto inkbubbles at the portion in contact with the nozzle 44 a is dischargedfrom nozzles 44 a as ink droplet i. As a result, the ink 4 is hit uponthe recording paper P.

At the ink discharge head 27, as shown in FIG. 8, a pair of heatingresistors 42 a, 42 b are provided substantially in parallel to eachother within one ink liquid chamber 45. Namely, a pair of heatingresistors 42 a, 42 b are provided within one ink liquid chamber 45.Further, at the ink discharge head 27, there are arranged plural sets ofheating resistors 42 a, 42 b provided substantially in parallel to eachother in a direction substantially perpendicular to carrying directionof the recording paper P indicated by arrow C in FIG. 11, i.e., in widthdirection of the recording paper P indicated by arrow W in FIG. 11. Inthis example, in FIG. 11, positions of the nozzles 44 a are indicated bysingle dotted lines.

As stated above, since the pair of heating resistors 42 a, 42 b takesuch shape to divide one resistor into two resistor portions so that thelengthy is the same and the width is halved, resistance values ofrespective resistors substantially become double value. In the casewhere resistors at these pairs of heating resistors 42 a, 42 b areconnected in series, there results the state where resistors havingresistance values of about double value are connected in series. Thus,resistance value thereof is four times greater than that of the resistorvalue before division.

Here, in order to boil ink 4 within the ink liquid chamber 45, it isnecessary to apply a predetermined pulse current to the pair of heatingresistors 42 a, 42 b to heat the pair of heating resistors 42 a, 42 b.By energy at the time of boiling, ink droplet i is discharged. Further,when resistance value is small, it is necessary to increase pulsecurrent caused to flow. However, since the pair of heating resistors 42a, 42 b caused to have a shape such that one resistor is divided intotwo resistor elements has high resistance value, it becomes possible tomake boiling by pulse current of small value.

Thus, at the ink discharge head 27, transistor for allowing pulsecurrent to flow, etc. can be reduced. As a result, reduction in spacecan be realized. It is to be noted that if a pair of heating resistors42 a, 42 b are formed so that thickness becomes small, resistance valuecan be further increased, but there is a predetermined limit forreducing the thickness of the pair of heating resistors 42 a, 42 b fromthe viewpoint of material selected as a pair of heating resistors 42 a,42 b and/or strength (durability) thereof, etc. For this reason,division is made without reducing the thickness to thereby increaseresistance values of the pair of heating resistors 42 a, 42 b.

Meanwhile, in discharging inks within the ink liquid chamber 45 fromnozzles 44 a, when drive control of a pair of heating resistors 42 a, 42b is performed so that time periods until ink within the ink liquidchamber 45 is boiled by a pair of heating resistors 42 a, 42 b, i.e.,bubble generation time periods are the same, ink droplet i is dischargedfrom nozzles 44 a toward the portion substantially immediately below. Inaddition, in the case where time difference takes place in bubblegeneration time of the pair of heating resistors 42 a, 42 b, it becomesdifficult to produce ink bubbles substantially at the same time on thepair of heating resistors 42 a, 42 b. As a result, ink droplet i isdischarged in the state shifted to any one of directions where a pair ofheating resistors 42 a, 42 b are arranged.

In concrete terms, as shown in FIG. 9, ink 4 is supplied by the ink flowpath 46 connected to the ink discharge head 27 so that ink 4 is filledwithin the ink liquid chamber 45. Further, as the result of the factthat pulse currents having the same current value are delivered to thepair of heating resistors 42 a, 42 b substantially at the same timing,the pair of heating resistors 42 a, 42 b are rapidly heatedsubstantially at the same time. As a result, ink bubbles B 1, B2 havingsubstantially the same volume are respectively produced at the ink 4 ofthe portion in contact with the pair of heating resistors 42 a, 42 b sothat ink 4 having a predetermined volume is pressed by expansion(swelling) of the ink bubbles B1, B2. Thus, at the ink discharge head27, as shown in FIG. 10, ink 4 having capacity equivalent to the ink 4pressed substantially vertically toward the recording paper P by the inkbubbles B1, B2 at the portion in contact with the nozzle 44 a isdischarged toward the portion substantially directly below from thenozzle 44 a as ink droplet i, and is hit upon the recording paper P.

Moreover, at the ink discharge head 27, as shown in FIG. 11, when pulsecurrents are delivered to the pair of heating resistors 42 a, 42 b atdifferent timings, ink bubbles B3, B4 are respectively produced atdifferent timings at ink 4 of the portion in contact with the pair ofheating resistors 42 a, 42 b. From this fact, by expansion (swelling)process by different timings of these ink bubbles B3, B4, ink 4 having apredetermined volume is pressed. Thus, at the ink discharge head 27, asshown in FIG. 12, ink droplet i is discharged in the state shiftedtoward ink bubbles having late bubble generation timing of ink bubblesB3, B4 in width direction of the recording paper P indicated by arrow Win FIG. 15 from the nozzle 44 a, and is hit onto the recording paper P.

In view of the above, in the present invention, in the case where supplytimings of pulse currents delivered to pair of heating resistors 42 a,42 b, reference pulse current is delivered to either one of heatingresistors of the pair of heating resistors 42 a, 42 b, and pulse currenthaving substantially the same current value as the reference pulsecurrent is delivered to the other heating resistor in the state wherethe time of the range within 20% of supply time of the reference pulsecurrent is shifted from the supply timing of the reference pulsecurrent.

Thus, at the ink discharge head 27, expansion (swelling) process bydifferent timings of ink bubbles B3, B4 formed on a pair of heatingresistors 42 a, 42 b becomes stable. As a result, it is possible tosuppress that discharge direction of ink droplet i is varied.

Moreover, at the ink discharge head 27, since different pulse currentsare delivered to a pair of heating resistors 42 a, 42 b at suitabletimings, it is possible to prevent inconvenience such that ink droplet icomes into contact with the edge of nozzle 44 a. Thus, it is possible tosuppress that discharge direction of the ink droplet i is varied.

The printer body 3 constituting the printer apparatus 1 to which thehead cartridge 2 constituted as described above is loaded will now beexplained with reference to the attached drawings.

The printer body 3 includes, as shown in FIGS. 1 and 13, a headcartridge loading portion 51 to which the head cartridge 2 is loaded, ahead cartridge holding mechanism 52 for holding/fixing the headcartridge 2 at the head cartridge loading portion 51, a head capopening/closing mechanism 53 for opening/closing the head cap, a paperfeed/eject mechanism 54 for performing paper feed/eject operation of therecording paper P, a paper feed opening 55 for feeding recording paper Pto the paper feed mechanism 54, and a paper eject opening 56 in whichrecording paper P is ejected from the paper feed/eject mechanism 54.

The head cartridge loading portion 51 is a recessed portion where thehead cartridge 2 is loaded, and is such that the head cartridge 2 isloaded so that the discharge surface 27 a of the ink discharge head 27and paper surface of the traveling recording paper P are substantiallyin parallel with each other in order to perform print operation inconformity with data onto traveling recording paper. The head cartridge2 is consumable supplies because there is the case where necessity ofexchange may take place owing to ink clogging within ink discharge head27, etc. For this reason, the head cartridge 2 is held by the headcartridge holding mechanism 52 so that it is detachable with respect tothe head cartridge loading portion 51.

The head cartridge holding mechanism 52 is a mechanism for detachablyholding the head cartridge 2 at the head cartridge loading portion 51.By holding knob 52 provided at the head cartridge 2 with respect tobiasing member such as spring, etc. (not shown) provided within holdinghole 52 b of the printer body 3, the head cartridge 2 can be held andfixed after undergone positioning in such a manner caused to be inpressure-contact with reference surface 3 a provided at the printer body3.

The head cap opening/closing mechanism 53 includes a drive unit foropening/closing head cap 28 of the head cartridge 2. When printoperation is performed, the head cap opening/closing mechanism 53 opensthe head cap 28 to allow the ink discharge head 27 to be exposed to therecording paper P. When print operation is completed, the head capopening/closing mechanism 53 closes the head cap 28 to protect the inkdischarge head 27.

A paper feed/eject mechanism 54 includes a drive portion for carryingthe recording paper P, and serves to carry the recording paper Pdelivered from the paper feed opening 55 up to ink discharge head 27 ofthe head cartridge 2 so that ink droplet i discharged from the nozzle 44a is hit to carry the printed recording paper P to the paper eject hole56 to eject it toward the external of the apparatus. The paper feed hole55 is an opening portion for supplying the recording paper P to thepaper feed/eject mechanism 54, and is adapted to have ability to stockplural recording papers P within the tray 55 a, etc. in a stackedmanner. The paper eject hole 56 is an opening portion in which inkdroplet i is hit to eject printed recording paper P.

A control circuit 61 shown in FIG. 14 for controlling print operation bythe printer apparatus 1 constituted as described above will now beexplained with reference to the attached drawings.

The control circuit 61 includes a printer drive unit 62 for performingdrive control of respective drive mechanisms 53, 54 of theabove-described printer body 3, a discharge control unit 63 forcontrolling current, etc. delivered to ink discharge heads 27corresponding to inks 4 of respective colors, a warning unit 64 forwarning the remaining quantities of inks 4 of respective colors, aninput/output terminal 65 for performing input/output operation of signalto and from the external equipment, a ROM (Read Only Memory) 66 in whichcontrol programs, etc. are recorded, a RAM (Random Access Memory) 67 fortemporarily storing control programs, etc. which have been read out sothat they are read out as occasion demands, and a control unit 68 forperforming controls of respective units.

The printer drive unit 62 drives drive motor constituting the head capopening/closing mechanism 53 on the basis of a control signal from thecontrol unit 68 to control the head cap opening/closing mechanism insuch a manner to open or close the head cap 28. Moreover, the printerdrive unit 62 drives the drive motor constituting the paper feed/ejectmechanism 54 on the basis of a control signal from the control unit 68to feed the recording paper P from the paper feed hole of the printerbody 3 to control the paper feed/eject mechanism in a manner to ejectthe recording paper P from the paper eject hole 56 after printingoperation.

As shown in FIG. 15, the discharge control unit 63 is an electriccircuit comprising a power supply 71 for allowing pulse currents to flowat a pair of heating resistors 42 a, 42 b respectively serving asresistors, switching elements 72 a, 72 b for respectively performingON/OFF operation of electric connection between the pair of heatingresistors 42 a, 42 b and the power supply 71, and a switching controlcircuit 73 for controlling switching operations of the switchingelements 72 a, 72 b.

The power supply 71 is connected to the heating resistors 42 a, 42 b andserves to allow pulse currents to flow at respective heating resistors.It is to be noted that while the power supply 71 may be used as powersupply for pulse current delivered to the electric circuit, pulsecurrent may be directly delivered from, e.g., control unit 68, etc.

The switching element 72 a is disposed between the heating resistor 42 aand the ground, and serves to control ON/OFF operation of pulse currentflowing in the heating resistor 42 a. The switching element 72 b isdisposed between the heating resistor 42 b and the ground, and serves tocontrol ON/OFF operation of pulse current flowing in the heatingresistor 42 b. Further, these switching elements 72 a, 72 b deliverpulse currents from the power supply 71 to the pair of heating resistors42 a, 42 b substantially at the same timing or at different timings asthe result of the fact that ON/OFF operations of respective switchingelements are switched.

The switching control circuit 73 is an electric circuit composed of,e.g., logic ICs and/or driver transistors, etc., and serves to switchON/OFF operations of the switching elements 72 a, 72 b to connect thepower supply 71 and the pair of heating resistors 42 a, 42 b to broughtthese heating resistors into ON state, or to ground the pair of heatingresistors 42 a, 42 b to brought these heating resistors into OFF state.Further, the switching control circuit 73 respectively switches ON/OFFoperations of the switching elements 72 a, 72 b to thereby controltimings at which pulse currents are respectively delivered to the pairof heating resistors 42 a, 42 b, or time periods during which pulsecurrent is delivered, etc.

At the discharge control unit 63 having a configuration as stated above,when the switching control circuit 73 turns the switching elements 72 a,72 b ON substantially at the same timing, pulse currents are bothdelivered to the pair of heating resistors 42 a, 42 b from the powersupply 71 substantially at the same timing. At this time, in the casewhere resistance values of the pair of heating resistors 42 a, 42 b aresubstantially the same, a pair of heating resistors 42 a, 42 b areheated substantially at the same timing when pulse currents aredelivered.

In this case, at the ink discharge head 27, as shown in FIG. 16A, sincea pair of heating resistors 42 a, 42 b are heated substantially at thesame timing, expansion (swelling) process of bubbles substantiallybecome the same. As a result, ink bubbles B1, B2 having substantiallythe same size are formed substantially at the same timing on the pair ofheating resistors 42 a, 42 b. Thus, ink droplets i are discharged towardthe portion substantially below from nozzles 44 a.

Then, explanation will be given in connection with the case where thedischarge control unit 63 controls the switching control circuit 73 insuch a manner to first turn the switching element 72 a ON tosubsequently turn the switching element 72 b ON in a delayed manner.

In this case, as shown in FIG. 16B, the discharge direction of inkdroplet i can be varied (adjusted) toward the heating resistor 42 sideof width direction W of the recording paper P. Namely, as the result ofthe fact that the switching element 72 a is first placed in ON state,pulse current is delivered to the heating resistor 42 a prior to theheating resistor 42 b. As a result, bubbles are produced on the heatingresistor 42 a prior to production thereof on the heating resistor 42 b.Further, expansion (swelling) process of ink bubbles B3 formed on theheating resistor 42 a is developed in a manner earlier than expansion(swelling) process of ink bubbles B4 formed on the heating resistor 42b. Thus, ink bubbles B3 having large volume are first formed. As aresult, inks 4 are pressed toward the heating resistor 42 b side todischarge ink droplets i from nozzles 44 a toward the heating resistor42 b side of width direction W of the recording paper P.

Here, according as shifts of ON timings of the switching elements 72 a,72 b are reduced, difference between generation timings of bubbles on apair of heating resistors 42 a, 42 b becomes small. Thus, dischargeangle (see FIG. 22) of ink droplets i discharged from nozzles 44 a withdischarge surface 27 a being as reference becomes large.

When there results less difference in expansion (swelling) process ofink bubbles B3, B4 formed on the pair of heating resistors 42 a, 42 b,volumetric difference between both bubbles is reduced. Thus, it ispossible to discharge ink droplets i so that they are hit at closerposition at the heating resistor 42 b side with respect to impact pointD when ink droplets i are discharged toward the portion substantiallyimmediately below from the nozzle 44 a.

On the other hand, according as shift between ON timings of theswitching elements 72 a, 72 b becomes large, difference betweengeneration timings of bubbles on the pair of heating resistors 42 a, 42b becomes large. As a result, discharge angle (see FIG. 22) of inkdroplets i discharged from the nozzles 44 a with the discharge surface27 a being as reference is reduced. Namely, when difference betweenexpansion (swelling) process of ink bubbles B3, B4 formed on the pair ofheating resistors 42 a, 42 b becomes large, volume difference betweenboth bubbles becomes large. Thus, it is possible to discharge inkdroplets i so that they are hit at farther position at the heatingresistor 42 b side with respect to impact point D when ink droplets iare discharged toward the portion substantially below from nozzles 44 a.

Further, at the discharge control unit 63, switching elements 72 a, 72 bare controlled by a switching control circuit 73 so that pulse currentdelivered to the heating resistor 42 a is caused to be reference, andpulse current is delivered to the heating resistor 42 b in the statewhere timing is shifted in a time of the range within 20% of the timeperiod during which pulse current is delivered to the heating resistor42 a with respect to the timing at which pulse current is delivered tothe heating resistor 42 a.

Then, explanation will be given in connection with the case where thedischarge control unit 63 controls the switching control circuit 73 insuch a manner to first turn the switching element 72 b ON tosubsequently turn the switching element 72 a ON in a delayed manner.

In this case, as shown in FIG. 16C, the discharge direction of inkdroplets i can be varied toward the heating resistor 42 a side of widthdirection W of the recording paper P. Namely, as the result of the factthat the switching element 72 b is first brought into ON state, pulsecurrent is delivered to the heating resistor 42 b prior to the heatingresistor 42 a. As a result, bubbles are produced on the heating resistor42 b prior to production thereof on the heating resistor 42 a. Further,expansion (swelling) process of ink bubbles B4 formed on the heatingresistor 42 a is developed in a manner earlier than expansion (swelling)process of ink bubbles B3 formed on the heating resistor 42 a. Thus, inkbubbles B4 having large volume is first formed. As a result, inks 4 arepressed toward the heating resistor 42 a side to discharge ink dropletsi from nozzles 44 a toward the heating resistor 42 a side of widthdirection W of recording paper P. Here, according as shift between ONtimings of switching elements 72 a, 72 b is reduced, difference betweengeneration timings of bubbles on the pair of heating resistors 42 a, 42b is reduced. Thus, discharge angle (see FIG. 22) of ink droplet idischarged from the nozzle 44 a with the discharge surface 72 a being asreference becomes large. This is similar to the case of FIG. 16B.Accordingly, when there results less difference in expansion (swelling)processes of ink bubbles B3, B4 formed on the pair of heating resistors42 a, 42 b similarly to the case of FIG. 16B, volume difference betweenboth bubbles becomes small. As a result, it is possible to discharge inkdroplets i so that they are hit at nearer position at the heatingresistor 42 b side with respect to impact point D when ink droplets iare discharged toward the portion substantially immediately below fromnozzles 44 a.

On the other hand, similarly to the case of FIG. 16B, according as shiftbetween ON timings of the switching elements 72 a, 72 b becomes large,difference between generation timings of bubbles on the pair of heatingresistors 42 a, 42 b becomes large. As a result, discharge angle (seeFIG. 22) of ink droplet i discharged from nozzle 44 a with the dischargesurface 27 a being as reference becomes small. Namely, when differencebetween expansion (swelling) processes of ink bubbles B3, B4 formed onthe pair of heating resistors 42 a, 42 b becomes large, volumedifference between both bubbles becomes large. As a result, it ispossible to discharge ink droplets i so that they are hit at fartherposition at the heating resistor 42 a side with respect to impact pointD when ink droplets i are discharged toward the portion immediatelybelow from the nozzles 44 a.

Further, at the discharge control unit 63, switching elements 72 a, 72 bare controlled by the switching control circuit 73 so that pulse currentdelivered to the heating resistor 42 b is caused to be reference, andpulse current is delivered to the heating resistor 42 a in the statewhere timing is shifted in a time of the range within 20% of time periodduring which pulse current is delivered to the heating resistor 42 bwith respect to timing at which pulse current is delivered to theheating resistor 42 b.

In a manner as stated above, at the discharge control unit 63, timingsof ON/OFF operations of switching elements 72 a, 72 b are controlled bythe switching control circuit 73, thereby making it possible to changedischarge direction from nozzles 44 a of ink droplets i toward adirection in which a pair of heating resistors 42 a, 42 b are providedin parallel, i.e., width direction W of the recording paper P.

Here, measurement result of discharge angle of the ink droplet i whenpulse current is delivered to the heating resistor 42 b in the statewhere timing is shifted (delayed) with respect to the heating resistor42 a with the time point when ink droplets i are discharged toward theportion immediately below from the nozzle 44 a being as reference isshown in FIG. 17.

In FIG. 17, shift quantity of supply timing of pulse current deliveredto the heating resistor 42 b is shown on the abscissa. In concreteterms, what percentage timing at which pulse current is delivered to theheating resistor 42 b is shifted in point of time with timing at whichpulse current is delivered to the heating resistor 42 a being asreference is shown.

In FIG. 17, discharge angle when discharge is made in the state wheredischarge direction is changed with the time at which ink droplets i aredischarged toward the portion substantially below from nozzles 44 a isshown on the ordinate. In FIG. 17, unlike FIG. 22, it is indicated thatdischarge angle when ink droplets i are hit toward the portionsubstantially immediately below is set to 0°, and according as dischargeangle is greatly shifted toward the heating resistor 42 b side so thatink droplets i are discharged, discharge angle becomes great. Formeasurement of the discharge angle, there is used ink discharge head 27in which thickness of the nozzle sheet is caused to be about 13μ and thediameter of nozzle 44 a is caused to be about 17 μm.

From the measurement result shown in FIG. 17, it is understood thatsupply timings of pulse currents with respect to a pair of heatingresistors 42 a, 42 b are shifted so that discharge direction of inkdroplets i discharged from nozzles 44 a are changed. In concreter terms,it is understood that when pulse current is delivered to the heatingresistor 42 b at a later (delayed) timing as compared to the heatingresistor 42 a, ink droplets i are discharged toward the heating resistor42 side.

Moreover, in FIG. 17, impact points D in which ink droplets i dischargedfrom nozzles 44 a are hit upon recording paper P when shift quantitiesof supply timings of the pulse current are 0%, 7.5%, 13%, 20%, 21%, 23%are caused to be samples 1 to 6. Further, the states of impact points Dof these samples 1 to 6 are shown in FIGS. 18A to 18F.

From evaluation results shown in FIGS. 18A to 18F, in samples 1 to 4 inwhich ink droplets i are discharged toward the heating resistor 42 b inthe state where supply timing of pulse current is delayed in the rangewithin 20% of supply time of pulse current of the heating resistor 42 awith respect to supply timing of pulse current to the heating resistor42 a, there is no unevenness at impact points D of ink droplets i evenafter the discharge direction has been changed. Accordingly, it isunderstood that ink droplets i are discharged from nozzles 44 a at apredetermined discharge angle.

Particularly, in samples 2 to 4 in which ink droplets i are dischargedtoward the heating resistor42 b in the state where supply timing ofpulse current is delayed within the range from 7.5% to 20% of supplytime of pulse current of the heating resistor 42 a with respect tosupply timing of pulse current to the heating resistor 42 a, changequantity of discharge angle with respect to shift quantity of supplytiming of pulse current is large. From this fact, the shift quantity ofsupply timing of pulse current is caused to be within the range from7.5% to 20%, thereby making it possible to stably perform control of thedischarge direction.

It is understood that in the range where shift quantity of supply timingof pulse current is above 20% (samples 5 and 6), unevenness takes placein impact points D of ink droplets i.

This is because it is considered that when shift quantity of supplytiming of pulse current is above 20%, balance of expansion (swelling)process of ink bubbles formed on a pair of heating resistors 42 a, 42 bis destroyed, and ink bubbles produced earlier resultantly become toolarger than ink bubbles produced later so that pressing state of ink 4by ink bubbles becomes unstable, and unevenness takes place in dischargedirection of ink droplets i discharged from nozzles 44 a.

Moreover, it is also considered that when shift quantity of supplytiming of pulse current is above 20%, discharge direction of ink dropleti discharged from nozzle 44 a becomes too oblique, so ink droplet icomes into contact with the edge of nozzle 44 a when ink droplet i isdischarged from nozzle 44 a so that unevenness takes place in dischargedirection. Accordingly, in the case of the samples 5 and 6, since impactpoints D of ink droplets i are varied, picture quality is lowered.

From facts as described above, in varying discharge direction of inkdroplet i discharged from nozzle 44 a, if control is made such thatshift quantity of supply timing of pulse current is caused to fallwithin 20% to deliver pulse current to the heating resistor 42 b, i.e.,if supply timing of pulse current to the heating resistor 42 b isdelayed in the range within 20% of supply time of pulse current of theheating resistor 42 a relative to supply timing of pulse current to theheating resistor 42 a, there is no unevenness in discharge direction ofink droplet i so that impact position of ink droplet i can bestabilized. It is understood that this is vey important from a viewpointof stabilizing impact position of ink droplet i.

Accordingly, in the above-described discharge control unit 63, theswitching control circuit 73 controls ON/OFF operations of switchingelements 72 a, 72 b so that when the discharge direction is varied todischarge ink droplet i from the nozzle 44 a, pulse current delivered toone of a pair of heating resistors 42 a, 42 b is caused to be reference,and supply timing of pulse current with respect to the other heatingresistor is shifted, on the other hand, in a time of the range within20% of supply time of pulse current serving as reference with respect tothe supply timing of pulse current serving as reference. Thus, at theprinter apparatus 1, it is possible to suppress unevenness of impactpositions of ink droplet i discharged in the state where dischargedirection is changed from nozzle 44 a. As a result, color toneunevenness and/or white stripe can be prevented. Thus, print operationcan be performed at excellent picture quality.

It is to be noted that while evaluation is made with timing at whichpulse current is delivered to heating resistor 42 a and supply time ofpulse current being as reference in the evaluations shown in FIGS. 17and 18, the present invention is not limited to such implementation,but, e.g., pulse current delivered to the heating resistor 42 b may becaused to be reference. In this case, ON/OFF operations of switchingelements 72 a, 72 b are controlled by the switching control circuit 73so that supply timing of pulse current to the heating resistor 42 a isshifted in the range within 20% of supply time of pulse current ofheating resistor 42 b relative to supply timing of pulse current to theheating resistor 42 b at the discharge control unit 63.

The warning unit 64 shown in FIG. 14 is display means, e.g., LCD (LiquidCrystal Display), etc. and serves to display information such as printcondition, print state and/or ink remaining quantity, etc. Moreover, thewarning unit 64 may be voice output means, e.g., speaker, etc. In thiscase, information such as print condition, print state and/or inkremaining quantity, etc. are outputted by voice. It is to be noted thatthe warning unit 64 may be caused to be of the configuration bothincluding display means and audio output means. In addition, suchwarning may be performed by monitor or speaker, etc. of informationprocessing equipment 69.

The input/output terminal 65 serves to transmit the above-describedinformation such as print condition, print state and/or ink remainingquantity, etc. to external information processing unit 69, etc. throughinterface. Moreover, the input/output terminal 65 is supplied, from theexternal information processing unit 69, etc., with control signal foroutputting the above-described information such as print condition,print state and/or ink remaining quantity, etc., and/or print data, etc.Here, the above-described information processing unit 69 is anelectronic equipment, e.g., personal computer or PDA (Personal DigitalAssistant), etc.

At the input/output terminal 65 connected to the information processingunit 69, etc., e.g., serial interface and/or parallel interface, etc.may be used as interface. In concrete terms, such interface is inconformity with the standard such as USB (Universal Serial Bus), RS(Recommended Standard) 232C, and/or IEEE (Institute of Electrical andElectronic Engineers) 1394, etc. Moreover, the input/output terminal 65may be adapted to perform data communication with the informationprocessing equipment 69 in any form such as wire communication orwireless communication. In this case, there are IEEE802.11a, 802.11b,802.11g, etc. as the wireless communication standard.

Network, e.g., Internet, etc. may intervene between the input/outputterminal 65 and the information processing equipment 69. In this case,the input/output terminal 65 is connected to network, e.g., LAN (LocalArea Network), ISDN (Integrated Service Digital Network), xDSL (DigitalSubscriber Line), FTHP (Fiber To The Home), CATV (Community AntennaTelevision), BS (Broadcasting Satellite), etc. The data communicationmay be performed by various protocols such as TCP/IP (TransmissionControl Protocol/Internet protocol), etc.

The ROM 66 is a memory, e.g., EP-ROM (Erasable Programmable Read-OnlyMemory), etc., and is adapted so that programs of respective processingthat the control unit 68 performs are stored. The stored programs areloaded into the RAM 67 by the control unit 68. The RAM 67 storesprograms which have been read out from the ROM 66 by the control unit68, and/or various states of the printer apparatus 1.

The control unit 68 controls respective units on the basis of print datainputted from the input/output terminal 65 and/or remaining quantitydata of ink 4 inputted from the head cartridge 2, etc. The control unit68 reads out, from the ROM 66, processing programs for controllingrespective units on the basis of an inputted control signal, etc. tostore those programs into the RAM 67 to perform controls and/orprocessing of respective units on the basis of the processing programs.

Namely, the control unit 68 controls the discharge control unit 63 onthe basis of processing programs, etc. stored in the ROM 66, etc. insuch a manner to allow, e.g., pulse current delivered to one of a pairof heating resistors 42 a, 42 b to be reference, and to shift, on theother hand, supply timing of pulse current to the other heating resistorin a time of the range within 20% of supply time of pulse currentserving as reference with respect to supply timing of pulse currentserving as reference so that discharge directions of ink droplets idischarged from nozzles 44 a are not varied.

It is to be noted that while processing programs are stored into the ROM66 in the control circuit 61 constituted as stated above, media forstoring processing program are not limited to ROM 66, but variousrecording media, e.g., optical disc, magnetic disc, magneto-optical discand/or IC card where processing programs are recorded, etc. may be used.In this case, the control circuit 61 may be caused to be of theconfiguration in which the control circuit 61 is connected, directly orthrough the information processing unit 69, to drive units for drivingvarious recording media to read out processing programs from theserecording media.

Here, the print operation of the printer apparatus 1 constituted asstated above will be explained with reference to the flowchart shown inFIG. 19. This operation is executed by arithmetic processing, etc. ofCPU (Central Processing Unit) which is not shown within the control unit68 on the basis of processing programs stored in memory means such asROM 66, etc.

First, in order that the printer apparatus 1 performs print operation,user operates operation (console) panel, etc. provided at the printerbody 3 to give instruction. Then, at step S1, the control unit 68 judgeswhether or not ink cartridges 11 of predetermined colors are loaded atrespective loading portions 22. Further, when ink cartridges 11 ofpredetermined colors are suitably loaded into all loading portions 22,processing by the control unit 68 proceeds to step S2. When the inkcartridges 11 are not suitably loaded at the loading portion 22,processing by the control unit 68 proceeds to step S4 to inhibit printoperation.

At step S2, the control unit 68 judges whether or not ink 4 within theconnecting portion 26 is less than a predetermined quantity, i.e., is ininkless state. When it is judged that current state is inkless state,the control unit 68 warns that effect (fact) at the warning unit 64 toinhibit print operation at step S4. On the other hand, when ink withinthe connecting unit 26 is the predetermined quantity or more, i.e., ink4 is filled, the control unit 68 permits print operation at step S3.

In performing print operation, the control unit 68 performs drivecontrol of respective drive mechanisms 53, 54 by the printer controlunit 62 to move the recording paper P up to the position where therecording paper P can be printed. In concrete terms, as shown in FIG.20, the control unit 68 drives drive motor constituting head capopening/closing mechanism 53 to move head cap 28 toward tray 55 a sidewith respect to the head cartridge 2 to allow nozzle 44 a of the inkdischarge head 27 to be exposed. Further, the control unit 68 drivesdrive motor which constitutes paper feed/eject mechanism 54 to travelrecording paper P. In concrete terms, the control unit 68 pulls (takes)out recording paper P by paper feed roller 81 from tray 55 a to carryone recording paper P which has been pulled (taken) out by a pair ofseparation rollers 82 a, 82 b rotating in directions opposite to eachother to inverting roller 83 to invert the carrying direction thereafterto carry the recording paper P to carrying belt 84 to control paperfeed/eject mechanism 54 in such a manner to allow holding means 85 tohold, at a predetermined position, recording paper P which has beencarried to the carrying belt 84 so that position where ink 4 is to behit is determined.

Further, when the control unit 68 confirms that the recording paper Phas been held at the print position, it controls the discharge controlunit 63 in such a manner to discharge ink droplets i toward therecording paper P from nozzles 44 a of the ink discharge head 27. Inconcrete terms, as shown in FIG. 16A, in the case where ink droplets iare discharged toward the portion substantially immediately below fromnozzles 44 a, the discharge control unit 63 is controlled so that pulsecurrents having substantially the same current value are delivered to apair of heating resistors 42 a, 42 b substantially at the same timing.Moreover, in the case where ink droplets i are discharged in the statewhere the discharge direction is changed toward the heating resistor 42b side from nozzles 44 a as shown in FIG. 16B, the control unit 68controls the discharge control unit 63 so that pulse current havingsubstantially the same current value as that of pulse current deliveredto the heating resistor 42 a is delivered to the heating resistor 42 bat timing later than timing at which pulse current is delivered to theheating resistor 42 a. Further, in the case where ink droplets i aredischarged in the state where the discharge direction is changed towardthe heating resistor 42 a side from nozzles 44 a as shown in FIG. 16C,the control unit 68 controls the discharge control unit 63 so that pulsecurrent having substantially the same current value as that of pulsecurrent delivered to the heating resistor 42 b is delivered to theheating resistor 42 a at timing later than timing at which pulse currentis delivered to the heating resistor 42 b.

Further, when ink droplets i are discharged from nozzles 44 a in thestate where the discharge direction is changed, the control unit 68controls the discharge control unit 63 so that pulse current deliveredto one of a pair of heating resistors 42 a, 42 b is caused to bereference, and pulse current is delivered to the other heating resistorin the state where timing is shifted in a time of the range within 20%of supply time of pulse current serving as reference with respect tosupply timing of pulse current serving as reference. Thus, at the inkdischarge head 27, it is possible to suppress unevenness of impactpositions of ink droplets i which have been discharged from nozzles 44 ain the state where the discharge direction has been changed. Thus, it ispossible to prevent color tone unevenness and/or white stripe.

As stated above, when ink droplets i are discharged from nozzles 44 a,ink 4 having the same quantity as quantity where ink droplets i aredischarged is immediately supplemented from the ink flow path 46 intothe ink liquid chamber 45, the state returns to the original state asshown in FIG. 6B. When ink droplets i are discharged from the inkdischarge head 27, the valve 34 e which closes opening portion 34 d ofthe ink chamber 34 b by biasing force of the biasing member 34 f andbiasing force of diaphragm 34 i is adapted so that in the case wherenegative pressure of ink 4 within the ink chamber 34 b of the inkflow-out path 34 c side divided into opening portion 34 d is increasedwhen ink droplets i are discharged from the ink discharge head 27 asshown in FIG. 6A, the diaphragm 34 i is pushed up by negative pressureof the ink 4 and atmospheric pressure. As a result, the valve 34 e ispushed up against biasing force of the biasing member 34 f along withvalve shaft 34 h. At this time, the opening portion 34 d between the inkflow-in path 34 a side and the ink flow-out path 34 c side of the inkchamber 34 b is opened. As a result, ink 4 is delivered from the inkflow-in path 34 a side toward the ink flow-out path 34 c side. Thus, ink4 is supplemented into ink flow path 46 of the ink discharge head 27.Further, negative pressure of ink 4 is lowered so that the diaphragm 34i returns to original form by restoring force to pull down the valve 34e along with the valve shaft 34 h by biasing force of the biasing member34 f so that the ink chamber 34 b is closed. In a manner as statedabove, at the valve mechanism 34, when negative pressure of ink 4 isincreased every time ink droplets i are discharged, the above-describedoperation will be repeated.

In a manner as stated above, characters and/or images corresponding toprint data in order with respect to recording paper P traveling by thepaper feed/eject mechanism 54. Further, the recording papers P in whichprint operation has been completed are ejected from paper eject hole 56by the paper feed/eject mechanism 54.

As explained above, in the liquid discharge apparatus and the liquiddischarge method according to the present invention, discharge controlis performed so that when ink droplets are discharged from the nozzlesin a manner to vary discharge direction, pulse current delivered to oneof heating resistors is caused to be reference, and pulse current isdelivered to the other heating resistor in the state where timing isshifted in a time of the range within 20% of supply time of pulsecurrent serving as reference with respect to supply timing of pulsecurrent serving as reference.

Thus, in the liquid discharge apparatus and the liquid discharge methodaccording to the present invention, it is possible to preventinconvenience such that when ink droplets are discharged from nozzles inthe state where the discharge direction is changed, the dischargedirection of ink droplets is varied, and/or inconvenience such that inkdroplets come into contact with the edge of nozzles so that dischargedirection is varied. As a result, it is possible to suppress unevennessof impact position of ink droplets discharged in the state wheredischarge direction has been varied from nozzles. Accordingly, in theliquid discharge apparatus and the liquid discharge method according tothe present invention, since variation of impact positions issuppressed, deterioration of picture quality resulting from color toneunevenness and/or white stripe, etc. is prevented. Thus, print operationcan be made at excellent picture quality.

In addition, in the liquid discharge apparatus and the liquid dischargemethod according to the present invention, since it is possible toprevent density unevenness of color and/or white stripe, etc. withoutprovision of overlap portion at the time of print operation as in theprior art, time required for print operation is greatly reduced, thusmaking it possible to print image of high quality.

It is to be noted that explanation has been given in the above-mentioneddescription by taking, as an example, ink discharge head 27 in whichpairs of heating resistors 42 a, 42 b are provided in parallel in widthdirection of recording paper P, the present invention is not limited tosuch a structure, but an ink discharge head adapted to control timingsof pulse currents delivered to plural pressure generating elements tothereby have ability to change discharge direction of ink droplet i canbe also applied to ink discharge heads 91, 101, 111 shown in FIGS. 21 to21C, for example. In this case, the ink discharge head 91 is adapted sothat a pair of heating resistors 92 a, 92 a are provided in parallel incarrying direction of recording paper P, the ink discharge head 101 isadapted so that three heating resistors 103 a, 103 b, 103 c are disposedwithin the ink liquid chamber 102, and the ink discharge head 111 isadapted so that four heating resistors 113 a, 113 b, 113 c, 113 d aredisposed within the liquid chamber 112.

1. A liquid discharge apparatus comprising discharge control meansincluding: a liquid chamber for storing liquid; two pressure generatingelements or more provided at the liquid chamber, and serving to pressliquid stored within the liquid chamber; and discharge holes fordischarging the liquid which has been pressed by the respective pressuregenerating elements in the state of droplet from the liquid chamber tocontrol supply timings and supply times of energies to the respectivepressure generating elements to control discharge angle when the dropletis discharged from the discharge hole, wherein the discharge controlmeans is adapted so that, with energy delivered to one of the respectivepressure generating elements being as reference, the discharge controlmeans delivers energy to the other pressure generating element in thestate where timing is shifted in a time of the range within 20% ofsupply time of energy serving as reference with respect to supply timingof energy serving as reference.
 2. The liquid discharge apparatus as setforth in claim 1, wherein the discharge control means delivers theenergy to the other pressure generating element at substantially thesame timing as that of the reference energy, or delivers the energy inthe state where time is shifted in the range from 7.5% to 20% of supplytime of the reference energy with respect to the reference energy. 3.The liquid discharge apparatus as set forth in claim 1, wherein thedischarge means is adapted so that the discharge holes are provided inparallel in substantially line form.
 4. A liquid discharge method for aliquid discharge apparatus including: a liquid chamber for storingliquid; two pressure generating elements or more provided at the liquidchamber, and serving to press liquid stored within the liquid chamber;and discharge holes for discharging the liquid which has been pressed bythe respective pressure generating elements in the state of droplet fromthe liquid chamber, wherein energy delivered to one of the respectivepressure generating elements is caused to be reference, and energy isdelivered to the other pressure generating element in a time of therange within 20% of supply time of energy serving as reference withrespect to supply timing of energy serving as reference to controldischarge angle when the droplet is discharged from the discharge hole.5. The liquid discharge method as set forth in claim 4, wherein theenergy is delivered to the other pressure generating element atsubstantially the same time timing as that of the reference energy, orthe energy is delivered thereto in the state where time is shiftedwithin the range from 7.5% to 20% of supply time of the reference energywith respect to the reference energy.
 6. The liquid discharge method asset forth in claim 4, wherein the discharge holes are provided inparallel in substantially line form.